Lamellar dissecting instrument

ABSTRACT

A microsurgical instrument that includes a handle and a dissecting tip coupled to the handle is disclosed. The tip includes a blade having a generally elliptical three-dimensional geometry. The blade may include an edge having a first arc and an opposing second arc. When the instrument is used to form an intracorneal pocket for the implantation of an intracorneal optical lens, the curvature of the first arc allows the edge to dissect a first blind spot of the pocket, and the curvature of the second arc allows the edge to dissect a second blind spot of the pocket. The blade may also be formed with a first depression in its top surface and a second depression in its bottom surface. When the instrument is used to form an intracorneal pocket, the depressions reduce the drag on, and corresponding trauma to, stromal tissue.

FIELD OF THE INVENTION

The present invention relates generally to ophthalmic microsurgicalinstruments and more specifically, but not by way of limitation, tomicrosurgical instruments suitable for creating a corneal pocketincision for the implantation of intracorneal optical lenses (ICOLs).

DESCRIPTION OF THE RELATED ART

The human eye in its simplest terms functions to provide vision bytransmitting light through a clear outer portion called the cornea, andfocusing the image by way of a crystalline lens onto a retina. Thequality of the focused image depends on many factors including the sizeand shape of the eye, and the transparency of the cornea and the lens.

The optical power of the eye is determined by the optical power of thecornea and the crystalline lens. In the normal, healthy eye, sharpimages are formed on the retina (emmetropia). In many eyes, images areeither formed in front of the retina because the eye is abnormally long(axial myopia), or formed in back of the retina because the eye isabnormally short (axial hyperopia). The cornea also may be asymmetric ortoric, resulting in an uncompensated cylindrical refractive errorreferred to as corneal astigmatism. In addition, due to age-relatedreduction in lens accommodation, the eye may become presbyopic resultingin the need for a bifocal or multifocal correction device.

In the past, axial myopia, axial hyperopia and corneal astigmatismgenerally have been corrected by spectacles or contact lenses, but thereare several refractive surgical procedures that have been investigatedand used since 1949. Barraquer investigated a procedure calledkeratomileusis that reshaped the cornea using a microkeratome and acryolathe. This procedure was never widely accepted by surgeons. Anotherprocedure that has been used is radial and/or transverse incisionalkeratotomy (RK or AK, respectively). Photoablative lasers have also beenused to reshape the surface of the cornea (photorefractive keratectomyor PRK) or for mid-stromal photoablation (Laser-Assisted In SituKeratomileusis or LASIK). All of these refractive surgical procedurescause an irreversible modification to the shape of the cornea in orderto effect refractive changes, and if the correct refraction is notachieved by the first procedure, a second procedure or enhancement mustbe performed. Additionally, the long-term stability of the correction isvariable because of the variability of the biological wound healingresponse between patients.

Permanent intracomeal implants made from synthetic materials are alsoknown for the correction of corneal refractive errors. Such implants maybe generally classified into two categories.

One category is intracorneal implants that have little or no refractivepower themselves, but change the refractive power of the cornea bymodifying the shape of the anterior surface of the cornea. U.S. Pat. No.5,123,921 (Werblin, et al.); U.S. Pat. Nos. 5,505,722, 5,466,260,5,405,384, 5,323,788, 5,318,047, 5,312,424, 5,300,118, 5,188,125,4,766,895, 4,671,276 and 4,452,235 owned by Keravision and directed tointrastromal ring devices; and U.S. Pat. No. 5,090,955 (Simon), U.S.Pat. No. 5,372,580 (Simon, et al.), and WIPO Publication No. WO 96/06584directed to Gel Injection Adjustable Keratoplasty (GIAK) all discloseexamples of this category of implant.

A second category is intracomeal implants having their own refractivepower. U.S. Pat. No. 4,607,617 (Choyce); U.S. Pat. No. 4,624,669(Grendahl); U.S. Pat. No. 5,628,794 (Lindstrom); and U.S. Pat. Nos.5,196,026 and 5,336,261 (Barrett, et al.) provide several examples ofthis category. In addition, U.S. patent application Ser. No. 08/908,230filed Aug. 7, 1997 entitled “Intracomeal Diffractive Lens”, which isincorporated herein in its entirety by reference, discloses an exampleof an ICOL that has both refractive and diffractive powers.

Microsurgical instruments used for the implantation of such intracornealimplants have also been developed. For example, WIPO Publication No. WO99/30645 owned by Keravision discloses a variety of instruments forsurgically implanting ring-shaped intracorneal implants and ICOLs. Thesetools may be used manually, but are preferably used in cooperation witha vacuum centering device. The surgical procedures described in thispublication require multiple instruments to form an intracomealring-shaped channel or an intracomeal pocket. In addition, the use of avacuum centering device increases the expense of the surgical procedure.

Accordingly, a need exists for a microsurgical instrument that moreeffectively creates an intracomeal pocket for the implantation of anICOL. The instrument should be easy for the surgeon to use, shouldmaximize patient safety, and should be economically feasible. Theinstrument should eliminate the need for multiple tools for forming theintracorneal pocket.

SUMMARY OF THE INVENTION

A preferred embodiment of the present invention is an ophthalmicmicrosurgical instrument that includes a handle and a dissecting tipcoupled to the handle. The tip includes a blade having a generallyelliptical three-dimensional geometry. The blade may include an edgehaving a first arc and an opposing second arc. When the instrument isused to form an intracorneal pocket, the curvature of the first arcallows the edge to dissect a first blind spot of the pocket, and thecurvature of the second arc allows the edge to dissect a second blindspot of the pocket. The blade may also be formed with a first depressionin its top surface and a second depression in its bottom surface. Whenthe instrument is used to form an intracomeal pocket, the depressionsreduce the drag on, and corresponding trauma to, stromal tissue.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and forfurther objects and advantages thereof, reference is made to thefollowing description taken in conjunction with the accompanyingdrawings in which:

FIG. 1 is a side view schematically illustrating a microsurgicalinstrument according to a preferred embodiment of the present invention;

FIG. 2 is an enlarged, side view of the dissecting tip of themicrosurgical instrument of FIG. 1;

FIG. 3 is an enlarged, top view of the dissecting tip of themicrosurgical instrument of FIG. 1; and

FIG. 4 is an enlarged, top view schematically illustrating the creationof an intracorneal pocket using the microsurgical instrument of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiment of the present invention and its advantages arebest understood by referring to FIGS. 1 through 4 of the drawings, likenumerals being used for like and corresponding parts of the variousdrawings.

FIG. 1 illustrates a microsurgical instrument 10 according to apreferred embodiment of the present invention. Instrument 10 ispreferably a lamellar dissecting tool for use in creating a cornealpocket incision for the implantation of intracorneal optical lenses(ICOLs). However, instrument 10 may be used for dissecting lamellartissue at locations other than the eye For convenience of description,but not by way of limitation, the present invention will be describedhereinbelow with reference to a lamellar dissecting instrument 10 foruse in creating a corneal pocket incision.

Instrument 10 includes a handle 12 and a dissecting tip 14. Handle 12preferably has a generally cylindrical geometry and preferably includesa region 16 having a knurled or roughened surface to facilitate thegripping of instrument 10. Handle 12 may also have a generally flatregion 18 that allows instrument 10 to be marked with identifying data.Handle 12 is preferably made out of conventional thermoset polymericmaterials. Dissecting tip 14 is coupled to a distal end 22 of handle 12.As shown in FIG. 1, such coupling is formed by an interference fitand/or epoxy. Alternatively, distal end 22 of handle 10 may include aconventional connecting hub (not shown) such as a collet or otherclamping mechanism for removably coupling with dissecting tip 14. Such aconnecting hub allows for the substitution of different blades or tipson instrument 10.

Dissecting tip 14 generally includes a neck 24 and a blade 26. Neck 24has a proximal portion 25 and a distal portion 27. Distal portion 27 andblade 26 preferably have a common longitudinal axis 28. Proximal portion25 and handle 12 preferably have a common longitudinal axis 29. Distalportion 27 preferably has a bend 30 to facilitate manipulation of blade26 by a surgeon. Bend 30 positions distal portion 27 and blade 26 at anangle a with respect to proximal portion 25 and handle 12. Angle α ispreferably from about 30 degrees to about 60 degrees, and is mostpreferably about 45 degrees. Blade 26 preferably has a length of about 4to about 5.5 mm, a maximum width of about 2 mm to about 3 mm, and amaximum thickness of about 0.48 mm. Most preferably, blade 26 has alength of about 4 mm, a maximum width of about 2 mm, and a maximumthickness of about 0.48 mm. Distal portion 27 of neck 24 preferably hasa length of about 6.5 mm to about 8 mm, a width of about 0.75 mm toabout 1 mm, and a thickness of about 0.48 mm. Most preferably, distalportion 27 of neck 24 has a length of about 8 mm, a width of about 0.75mm, and a thickness of about 0.48 mm. Proximal portion 25 of neck 24preferably has a length of about 10.3 mm, a width of about 2.8 mm, andthickness of about 0.6 mm. The length of dissecting tip 14 from thedistal end of blade 26 to bend 30 is preferably about 10 mm to about10.5 mm. Most preferably, this length is about 10 mm. Neck 24 and blade26 are preferably integrally formed from surgical stainless steel orother conventional material used for microsurgical instrument blades.

Neck 24 and blade 26 are more clearly shown in the enlarged, side viewof FIG. 2 and the enlarged, top view of FIG. 3. Blade 26 preferably hasa generally elliptical, three dimensional geometry with a depression 32on its top surface and a depression 34 on its bottom surface. As shownin FIG. 3, depression 32 preferably has a generally elliptical shapefrom a top view. Similarly, depression 34 preferably has a generallyelliptical shape from a bottom view. Alternatively, blade 26 may beformed without depressions 32 and 34, if desired. Blade 26 has an edge36 formed around its periphery. Edge 36 is preferably formed so that itis sharp enough to easily delaminate layers of corneal stroma duringcreation of an intracorneal pocket, but not sharp enough to easily cutthe stromal tissue. Edge 36 is preferably formed with an edge radiusbetween about 0.001 inches to about 0.025 inches, and more preferablyabout 0.005 inches. Depression 32 and edge 36 define a generallyelliptical, convex, ring shaped surface 37 for contacting anddelaminating the stromal tissue. Similarly, depression 34 and edge 36define a generally elliptical, convex, ring shaped surface 39 (notshown) for contacting and delaminating the stromal tissue. It has beenfound that when blade 26 having depressions 32 and 34 is used to createan intracomeal pocket, it exhibits less drag or friction on stromaltissues than a similarly shaped blade having no depressions 32 and 34.Reducing such drag correspondingly reduces the trauma to the stromaltissues, as well as the chance of accidentally tearing the stromaltissues.

Edge 36 preferably comprises three arcs 38, 40, and 42. Arc 38 includesthe portion of edge 36 between a point 44 proximate distal portion 27 ofneck 24 to a point 46 proximate a distal end of blade 26. Arc 38preferably has a length of about 3.7 mm to about 5.2 mm. For example, inan intracomeal pocket having a diameter of about 8 mm that is createdusing a tunnel incision having a width of about 3 mm, blade 26 may havea length of about 4 mm, a width of about 2 mm, and an arc 38 having alength of about 3.7 mm. This length of arc 38 may be defined by moving aradius of curvature of about 4 mm through an angle of rotation of about53.4 degrees. As another example, in an intracorneal pocket having adiameter of about 8 mm that is created using a tunnel incision having awidth of about 3 mm, blade 26 may have a length of about 5.5 mm, a widthof about 3 mm, and an arc 38 having a length of about 5.2 mm. Thislength of arc 38 may be defined by moving a radius of curvature of about4 mm through an angle of rotation of about 74.2 degrees. Arc 40generally opposes arc 38 and includes the portion of edge 36 between apoint 48 proximate distal portion 27 of neck 24 and a point 50 proximatethe distal end of blade 26. Arc 40 preferably has an identical length,and is preferably formed in an identical manner, as arc 38. Arc 42includes the portion of edge 36 between points 46 and 50. Arc 42prevents blade 26 from having a sharp distal tip that would be prone tocut, instead of delaminate, stromal tissue. The length of arc 42 isdependent on the separation between arcs 38 and 40. For example, ifblade 26 has a width of about 2 mm, arc 42 preferably has a length ofabout 1.9 mm. This length may be defined by moving a radius of curvatureof about 0.8 mm through an angle of rotation of about 138 degrees. Asanother example, if blade 26 has a width of about 3 mm, arc 42preferably has a length of about 2.0 mm. This length may be defined bymoving a radius of curvature of about 1.0 mm through an angle ofrotation of about 114 degrees.

Referring now to FIGS. 1-4, the preferred method of using lamellardissecting instrument 10 to create an intracomeal pocket for theinsertion of an ICOL will now be described in greater detail. As shownin FIG. 4, a human eye has a cornea 60 having a diameter of about 12 mm.Therefore, the diameter of an ICOL (not shown) must be less than 12 mm,is preferably from about 5 mm to about 9 mm, and is most preferablyabout 7 mm. Intracorneal pocket 62 for receiving the ICOL preferably hasa diameter about 1 mm larger than the diameter of the ICOL. For thepreferred ICOL having a diameter of about 7 mm, intracorneal pocket 62has a diameter of about 8 mm. For convenience of description, but not byway of limitation, the preferred method of creating an intracomealpocket with lamellar dissecting instrument 10 will be described withreference to an intracomeal pocket 62 having a diameter of about 8 mm.

During the procedure, a surgeon uses an operating microscope tovisualize the anterior aspect of eye. The surgeon first applies atopical anesthetic to the eye. A fine Thorton ring, a Kremer forceps, orsimilar conventional instrument is used to secure the eye from rotating.A conventional 8 mm optical zone marker is placed on the cornea centeredon the visual axis of the eye. A conventional 3 mm optical zone markeris placed on the cornea adjacent the 8 mm optical zone marker,preferably at the twelve o'clock position. The surgeon determines thethickness of cornea 60 at a center 63 of the 3 mm optical zone markusing conventional ultrasound pachyrnetry. The surgeon then sets aconventional surgical diamond knife to about sixty percent of thepachymetry reading, and makes an incision parallel to the limbus atcenter 63. The surgeon creates a tunnel incision 64 into cornea 60 atcenter 63 using a Paufique Duredge knife, Suarez spreader, or similarconventional instrument. Tunnel incision 64 preferably has a width ofabout 3 mm, a length of about 1.5 mm, and a depth of about 0.25 mm toabout 0.3 mm from the outer surface of cornea 60. The depth of tunnelincision 64 is preferably selected to dispose edge 36 of blade 26 atabout the midplane of the desired intracorneal pocket 62. The surgeonremoves the knife used to create tunnel incision 64, and inserts tip 14of instrument 10 into tunnel incision 64, with edge 36 of blade 26 beingdisposed on the midplane of the desired pocket 62. Tip 14 preferablydoes not enlarge tunnel incision 64.

The surgeon then creates intracomeal pocket 62 using a series ofarcuate, planar movements of tip 14. Because of the width of distalportion 27 of neck 24, the arcuate movements of tip 14 do not result inneck 24 contacting the sides of tunnel incision 64, avoiding trauma tostromal tissue. Due to the length of blade 26 and distal portion 27 ofneck 24, tip 14 may easily reach the desired distal end 66 of pocket 62.In addition, due to the curvature of arcs 38 and 40, tip 14 can be usedto create a circular pocket 62 even at “blind spots” 68 and 70, whichare indicated by asterisks in FIG. 4. Edge 36 and surfaces 37 and 39function primarily to dissect or delaminate stromal tissue. Depressions32 and 34 function primarily to reduce the drag on, and associatedtrauma to, stromal tissue.

After formation of pocket 62, the surgeon removes tip 14 of instrument10, and then implants an ICOL into pocket 62 using forceps or a similarconventional instrument. A topical antibiotic/steroid solution is placedin the eye after implantation. If the explanting of the ICOL isnecessary at a later time, arc 42 of blade 26 is preferably sharp enoughto re-open tunnel incision 64 after the incision has healed.

From the above, it may be appreciated that the present inventionprovides a microsurgical instrument that more effectively creates anintracomeal pocket for the implantation and explantation of an ICOL. Theinstrument is easy for the surgeon to use and is relatively inexpensive.The instrument eliminates the need for multiple tools for forming theintracomeal pocket, simplifying the surgical procedure and maximizingpatient safety.

The present invention is illustrated herein by example, and variousmodifications may be made by a person of ordinary skill in the art. Forexample, the length of blade 26 and neck 24 may be changed toaccommodate the formation of intracomeal pockets having variousdiameters. As another example, the geometries of handle 12 and neck 24may be different from that shown in the preferred embodiment. As afurther example, the three dimensional geometry of blade 26 may be ashape other than an ellipse, as long as blade 26 has a generallyelliptical shape from a top view. As a final example, although thepreferred instrument is described hereinabove as a lamellar dissectinginstrument for the implantation of an ICOL, the present invention isapplicable to instruments used for dissecting lamellar tissue atlocations other than the eye

It is believed that the operation and construction of the presentinvention will be apparent from the foregoing description. While theapparatus and methods shown or described above have been characterizedas being preferred, various changes and modifications may be madetherein without departing from the spirit and scope of the invention asdefined in the following claims.

What is claimed is:
 1. An ophthalmic microsurgical instrument,comprising: a handle; a dissecting tip coupled to said handle, said tipcomprising a blade having a generally elliptical, non-sphericalthree-dimensional geometry, wherein said blade comprises a firstdepression on a top surface and a second depression on a bottom surface.2. The instrument of claim 1 wherein said blade comprises an edge havinga first arc an opposing second arc.
 3. The instrument of claim 2wherein: said instrument is for creating a generally circularintracomeal pocket; a curvature of said first arc allows said edge todissect a first blind spot of said pocket; and a curvature of saidsecond arc allows said edge to dissect a second blind spot of saidpocket.
 4. The instrument of claim 1 wherein: said first and seconddepressions reduce a drag on stromal tissue when said instrument is usedto create an intracorneal pocket.
 5. A method of creating a generallycircular intracomeal pocket for the implantation of an intracornealoptical lens, comprising the steps of: providing an instrument having ahandle and a dissecting tip, said tip comprising a blade having an edgewith a generally elliptical, non-circular shape, said shape comprising afirst arc and an opposing second arc; inserting said tip into anincision into a cornea; creating said pocket by moving said tip in anarcuate, planar manner so as to dissect stromal tissue.
 6. The method ofclaim 5 wherein said creating step comprises: dissecting a first blindspot of said pocket proximate said incision with said first arc; anddissecting a second blind spot of said pocket proximate said incisionwith said second arc.
 7. A method of creating a generally circularintracorneal pocket for the implantation of an intracorneal opticallens, comprising the steps of: providing an instrument having a handleand a dissecting tip, said tip comprising a blade having a generallyelliptical, non-spherical three-dimensional geometry with a firstdepression in a top surface and a second depression in a bottom surface;inserting said tip into an incision into a cornea; creating said pocketby moving said tip in an arcuate, planar manner so as to dissect stromaltissue.
 8. The method of claim 7 wherein, during said creating step,said first and second depressions reduce a drag on said stromal tissue.9. A dissecting tip for an ophthalmic microsurgical instrument forcreating an intracorneal pocket, comprising: a blade having a generallyelliptical, non-spherical three-dimensional geometry, a first depressionon a top surface, and a second depression on a bottom surface.